U.S. patent number 5,415,901 [Application Number 08/069,520] was granted by the patent office on 1995-05-16 for laser ablation device and thin film forming method.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Yukio Nishikawa, Youichi Ohnishi, Kunio Tanaka, Yoshikazu Yoshida.
United States Patent |
5,415,901 |
Tanaka , et al. |
May 16, 1995 |
Laser ablation device and thin film forming method
Abstract
A laser ablation device for forming a thin film includes a
vacuum chamber having a gas introduction port through which an
oxidating gas is introduced into the chamber, and a
light-transmittable section, a target holder disposed in the vacuum
chamber for holding a target made of a film forming material of an
oxide, an object holder confronting the target holder for holding
an object on which the thin film is to be formed, a short
wavelength laser which emits a first short wavelength laser light
passing to the target in the vacuum chamber through the
light-transmittable section from outside of the vacuum chamber, and
a short wavelength laser light irradiating device for irradiating
the object with a second short wavelength laser light passing into
the vacuum chamber through the light-transmittable section from
outside of the vacuum chamber. The second short wavelength laser
light has an intensity lower than that of the first short
wavelength laser light irradiating the target. Alternatively, a
short wavelength laser light passing device causes the second short
wavelength laser light to pass through the light-transmittable
section from outside of the vacuum chamber and then to pass in the
vicinity of a surface of the object in the vacuum chamber as
approximately parallel to the surface of the object.
Inventors: |
Tanaka; Kunio (Osaka,
JP), Ohnishi; Youichi (Higashiosaka, JP),
Yoshida; Yoshikazu (Izumi, JP), Nishikawa; Yukio
(Ikeda, JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP)
|
Family
ID: |
15273718 |
Appl.
No.: |
08/069,520 |
Filed: |
June 1, 1993 |
Foreign Application Priority Data
|
|
|
|
|
Jun 1, 1992 [JP] |
|
|
4-140656 |
|
Current U.S.
Class: |
427/596; 118/50;
427/128; 427/561; 427/599; 427/597; 427/586; 427/294; 118/715 |
Current CPC
Class: |
C23C
14/0021 (20130101); C23C 14/28 (20130101); C30B
23/002 (20130101); H01F 41/205 (20130101); H01F
10/20 (20130101) |
Current International
Class: |
C23C
14/00 (20060101); C23C 14/28 (20060101); C30B
23/02 (20060101); H01F 10/20 (20060101); H01F
41/14 (20060101); H01F 41/20 (20060101); H01F
10/10 (20060101); H01F 010/02 () |
Field of
Search: |
;427/128-132,561,586,599,596,597,294 ;118/715,50 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
5017277 |
May 1991 |
Yoshida et al. |
5065697 |
November 1991 |
Yoshida et al. |
5082545 |
January 1992 |
Tanaka et al. |
5159169 |
October 1992 |
Nishikawa et al. |
|
Other References
Komuro et al., "Preparation of High-T.sub.c Superconducting Films
by Q-Switched YAG Laser Sputtering", Japanese Journal of Applied
Physics, vol. 27, No. 1, Jan. 1988, pp. L34-L36..
|
Primary Examiner: Pianalto; Bernard
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
We claim:
1. A laser ablation device for forming a thin film, said device
comprising:
a vacuum chamber having a discharge port through which the chamber
is evacuated, a gas introduction port through which an oxidating
gas is introduced into the chamber, and a light-transmittable
section;
a target holder disposed in the vacuum chamber;
a target, from which a film is to be formed, held by said target
holder, said target comprising an oxide;
an object holder confronting the target holder;
a short wavelength laser disposed outside of said vacuum chamber at
such a position as to emit a first short wavelength laser light
passing through the light-transmittable section from outside of the
vacuum chamber and onto said target in the vacuum chamber; and
short wavelength laser light irradiating means for irradiating an
object held by the object holder in the vacuum chamber with short
wavelength laser light passing through the light-transmittable
section from outside of the vacuum chamber, the second short
wavelength laser light having an intensity lower than that of the
first short wavelength laser light irradiating the target.
2. The laser ablation device as claimed in claim 1, wherein the
second short wavelength laser light irradiating the object has an
intensity of at most 1/10 of that of the first short wavelength
laser light irradiating the target.
3. The laser ablation device as claimed in claim 1, wherein the
oxide is a ferrite, and the second short wavelength laser light
irradiating the object has an intensity of 1/10 of that of the
first short wavelength laser light irradiating the target.
4. The laser ablation device as claimed in claim 1, wherein a
single short wavelength laser emits both the first short wavelength
laser light and the second short wavelength laser light, and said
irradiating means is an optical system which splits short
wavelength laser light from the short wavelength laser into the
first and second short wavelength laser lights.
5. A laser ablation device for forming a thin film, said device
comprising:
a vacuum chamber having a discharge port through which the chamber
is evacuated, a gas introduction port through which an oxidating
gas is introduced into the chamber, and a light-transmittable
section;
a target holder disposed in the vacuum chamber;
a target, from which a film is to be formed, held by said target
holder, said target comprising an oxide;
an object holder confronting the target holder;
a short wavelength laser disposed outside of said vacuum chamber at
such a position as to emit a first short wavelength laser light
passing through the light-transmittable section from outside of the
vacuum chamber and onto said target in the vacuum chamber; and
short wavelength laser light passing means for causing a second
short wavelength laser light to pass from outside of the vacuum
chamber through the light-transmittable section and to pass in the
vicinity of a surface of an object held by the object holder in the
vacuum chamber as approximately parallel to the surface, the second
short wavelength laser light having an intensity lower than that of
the first short wavelength laser light irradiating the target.
6. The laser ablation device as claimed in claim 5, wherein the
second short wavelength laser light irradiating the object has an
intensity of at most 1/10 of that of the first short wavelength
laser light irradiating the target.
7. The laser ablation device as claimed in claim 5, wherein the
oxide is a ferrite, and the second short wavelength laser light
irradiating the object has an intensity of 1/10 of that of the
first short wavelength laser light irradiating the target.
8. The laser ablation devices as claimed in claim 5, wherein a
single short wavelength laser emits both the first short wavelength
laser light and the second short wavelength laser light, and said
passing means is an optical system which splits short wavelength
laser light from the short wavelength laser into the first and
second short wavelength laser lights.
9. A method for forming a thin film on an object, said method
comprising:
generating a vacuum in a vacuum chamber;
placing an object in the vacuum chamber;
providing a target comprising a soft magnetic oxide in the vacuum
chamber;
introducing an oxidating gas into the vacuum chamber;
directing a first short wavelength laser light onto the target in
the vacuum chamber; and
irradiating the object in the vacuum chamber with a second short
wavelength laser light having an intensity lower than that of the
first short wavelength laser light irradiating the target.
10. A method for forming a thin film on an object, said method
comprising:
generating a vacuum in a vacuum chamber;
placing an object in the vacuum chamber;
providing a target comprising a soft magnetic oxide in the vacuum
chamber;
introducing an oxidating gas into the vacuum chamber;
directing a first short wavelength laser light onto the target in
the vacuum chamber; and
passing a second short wavelength laser light in the vicinity of a
surface of the object in the vacuum chamber as approximately
parallel to the surface of the object, the second short wavelength
laser light having an intensity lower than that of the first short
wavelength laser light irradiating the target.
11. A laser ablation device for forming a thin film, said device
comprising:
a vacuum chamber having a discharge port through which the chamber
is evacuated, a gas introduction port through which an oxidating
gas is introduced into the chamber, and a light-transmittable
section;
a target, from which a film is to be formed, disposed in the vacuum
chamber, said target comprising an oxide;
an object holder confronting the target;
a short wavelength laser disposed outside of said vacuum chamber at
such a position as to emit a first short wavelength laser light
passing through the light-transmittable section from outside of the
vacuum chamber and onto said target in the vacuum chamber; and
short wavelength laser light irradiating means for irradiating an
object held by the object holder in the vacuum chamber with short
wavelength laser light passing through the light-transmittable
section from outside of the vacuum chamber, the second short
wavelength laser light having an intensity lower than that of the
first short wavelength laser light irradiating the target.
12. The laser ablation device as claimed in claim 11, wherein the
second short wavelength laser light irradiating the object has an
intensity of at most 1/10 of that of the first short wavelength
laser light irradiating the target.
13. The laser ablation device as claimed in claim 11, wherein the
oxide is a ferrite, and the second short wavelength laser light
irradiating the object has an intensity of 1/10 of that of the
first short wavelength laser light irradiating the target.
14. The laser ablation device as claimed in claim 11, wherein a
single short wavelength laser emits both the first short wavelength
laser light and the second short wavelength laser light, and said
irradiating means is an optical system which splits short
wavelength laser light from the short wavelength laser into the
first and second short wavelength laser lights.
15. A laser ablation device for forming a thin film, said device
comprising:
a vacuum chamber having a discharge port through which the chamber
is evacuated, a gas introduction port through which an oxidating
gas is introduced into the chamber, and a light-transmittable
section;
a target, from which a film is to be formed, disposed in said
vacuum chamber, said target comprising an oxide;
an object holder disposed in the vacuum chamber;
a short wavelength laser disposed outside of said vacuum chamber at
such a position as to emit a first short wavelength laser light
passing through the light-transmittable section from outside of the
vacuum chamber and onto said target in the vacuum chamber; and
short wavelength laser light passing means for causing a second
short wavelength laser light to pass from outside of the vacuum
chamber through the light-transmittable section and to pass in the
vicinity of a surface of an object held by the object holder in the
vacuum chamber as approximately parallel to the surface, the second
short wavelength laser light having an intensity lower than that of
the first short wavelength laser light irradiating the target.
16. The laser ablation device as claimed in claim 15, wherein the
second short wavelength laser light irradiating the object has an
intensity of at most 1/10 of that of the first short wavelength
laser light irradiating the target.
17. The laser ablation device as claimed in claim 15, wherein the
oxide is a ferrite, and the second short wavelength laser light
irradiating the object has an intensity of 1/10 of that of the
first short wavelength laser light irradiating the target.
18. The laser ablation device as claimed in claim 15, wherein a
single short wavelength laser emits both the first short wavelength
laser light and the second short wavelength laser light, and said
passing means is an optical system which splits short wavelength
laser light from the short wavelength laser into the first and
second short wavelength laser lights.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a laser ablation device for
forming a thin film by means of a short wavelength laser light, and
more particularly, to a laser ablation device for forming a soft
magnetic thin film of an oxide.
A conventional example of a laser ablation device for forming an
oxide thin film using a short wavelength laser light is described
in Japanese Journal of Applied Physics, vol. 27 (1988) by S. Komuro
et al. The constitution of the prior art will be described with
reference to FIG. 6.
The conventional laser ablation device for forming a thin film
includes a target holder 41' for holding a target 41 of the
sintered body of Ni-Zn-ferrite as an oxide film forming material,
and a substrate holder 42 (holder for an object on which a film is
to be formed) confronting the target holder 41' to hold a substrate
43 (the object on which a film is to be formed) in a vacuum chamber
40. The vacuum chamber 40 has a discharging device 49, a gas
introduction port 48, and a light-transmittable window 47. A short
wavelength laser light 45 having a wavelength of 532 nm, which is
the second higher harmonic laser light of a YAG laser 44 performing
Q switching of a visible light and placed outside the vacuum
chamber 40, is condensed by an optical system 46 and irradiates the
target 41 through the light-transmittable window 47. A heater 42'
is built into the substrate holder 42 to heat the substrate 43 to a
predetermined temperature.
The operation of the above-described laser ablation device will be
discussed with reference to FIG. 6.
In FIG. 6, after the vacuum chamber 40 is evacuated by the
discharging device 49, O.sub.2 gas or N.sub.2 O gas is introduced
into the chamber 40 from the gas introduction port 48. The short
wavelength laser light 45 irradiates the target 41. As a result,
ablated particles are projected from the sintered body of
Ni-Zn-ferrite constituting the target 41 owing to the energy of the
short wavelength laser light, and a thin film of Ni-Zn-ferrite is
formed on the substrate 43 held by the substrate holder 42 opposed
to the target 41.
At the time the thin film is formed, since the substrate 43 is
heated to a predetermined temperature by the built-in heater 42' of
the substrate holder 42, and an oxidating gas such as O.sub.2 gas
or N.sub.2 O gas is introduced in the chamber 40 from the gas
introduction port 48, the Ni-Zn-ferrite thin film formed on the
substrate 43 reacts with the oxygen, whereby the oxygen deficiency
of the Ni-Zn-ferrite thin film is reduced.
However, for an oxide of many components such as those represented
by Ni-Zn-ferrite, the oxygen reacts only to a little extent and the
oxygen deficiency of the thin film cannot be sufficiently reduced.
Therefore, the prior art is capable of forming a thin film of high
coercive force only.
In the event that the thin film of Ni-Zn-ferrite or the like formed
by the conventional laser ablation device is to be employed as a
soft magnetic film of low coercive force, it becomes necessary to
impart characteristics to the film by which the film will exhibit
lower coercive force. More specifically, the oxidation state of the
thin film (valence, etc.) must be precisely adjusted to thereby
sufficiently reduce the oxygen deficiency. For this purpose, the
substrate 43 with the thin film has been conventionally heated
under an oxidation atmosphere at high temperatures (for example,
800.degree. C. or higher) and annealed for several hours.
Therefore, a large number of processing steps are needed
accompanied by the cost associated therewith.
Moreover, the above-mentioned annealing at high temperatures cannot
be applied to a thin film head because the material of the head
cannot withstand temperatures higher than 350.degree. C. In other
words, the conventional laser ablation device is useless when a
thin film head is to be manufactured.
SUMMARY OF THE INVENTION
The object of the present invention is, therefore, to provide a
laser ablation device which can control the crystalline state
(including the oxidation state or the like) of a formed film at
relatively low temperatures, while sufficiently reducing the oxygen
deficiency of the film without requiring high-temperature annealing
to improve the oxidation state, thereby eliminating the
above-described drawbacks of the prior art.
In accomplishing these and other objects, according to a first
aspect of the present invention, there is provided a laser ablation
device for forming a thin film and which comprises: a vacuum
chamber connected to a discharging device for creating a vacuum in
the chamber and having a gas introduction port through which an
oxidating gas is introduced into the chamber, and a
light-transmittable section; a target holder disposed in the vacuum
chamber for holding a target made of a film forming material of an
oxide; an object holder confronting the target holder for holding
an object; a short wavelength laser which emits a first short
wavelength laser light passing from outside of the vacuum chamber
to the target in the vacuum chamber through the light-transmittable
section; and a short wavelength laser light irradiating device for
irradiating the object held by the object holder in the vacuum
chamber with a second short wavelength laser light passing through
the light-transmittable section from outside of the vacuum chamber,
the second short wavelength laser light having an intensity lower
than that of the first short wavelength laser light irradiating the
target.
According to the first aspect of the present invention, when the
first short wavelength laser light irradiates the target inside the
vacuum chamber into which the oxidating gas has been introduced,
ablated particles of the film forming material constituting the
target are projected from the target and migrate over the object
held by the object holder, thereby forming a thin film. During this
time, a second short wavelength laser light of an intensity lower
than that of the first short wavelength laser light irradiating the
target is directed onto the object via the light-transmittable
section. Therefore, the migrating ablated particles are excited to
readily react with the oxidating gas in the vicinity of the object,
thus accelerating the oxygen reaction and the oxidation of the
film. The oxygen deficiency of the formed film is hence reduced and
the crystallizability of the film is improved.
According to a second aspect of the present invention, there is
provided a laser ablation device for forming a thin film and which
comprises: a vacuum chamber connected to a discharging device for
creating a vacuum in the chamber and having a gas introduction port
through which an oxidating gas is introduced into the chamber, and
a light-transmittable section; a target holder disposed in the
vacuum chamber for holding a target made of a film forming material
of an oxide; an object holder confronting the target holder for
holding an object; a short wavelength laser which emits a first
short wavelength laser light passing from outside of the vacuum
chamber to the target in the vacuum chamber through the
light-transmittable section; and a short wavelength laser light
passing device for causing a second short wavelength laser light to
pass through the light-transmittable section from outside of the
vacuum chamber and to pass in the vicinity of a surface of the
object held by the object holder in the vacuum chamber as
approximately parallel to the surface of the object, the second
short wavelength laser light having an intensity lower than that of
the first short wavelength laser light irradiating the target.
When the first short wavelength laser light irradiates the target
in the vacuum chamber into which the oxidating gas has been
introduced, ablated particles of the film forming material
constituting the target project from the target and migrate over
the object held by the object holder thereby forming a thin film.
At this time, since the second short wavelength laser light is
guided approximately parallel to the surface of the object in the
vicinity of the surface of the object, the second short wavelength
laser light irradiates the ablated particles before the particles
reach the object, and accordingly, the ablated particles are
excited to readily react with the oxidating gas in the vicinity of
the object. Therefore, the oxidation is accelerated and the oxygen
deficiency of the formed film is reduced, and moreover, the
oxidating gas in the vicinity of the object is irradiated by the
second short wavelength laser light to be dissociated to produce O
radicals. The oxidation with the ablated particles is enhanced, and
the oxidation of the formed film is accelerated, the oxygen
deficiency of the formed film is reduced and the crystallizability
is improved.
According to a further aspect of the present invention, the short
wavelength laser light irradiating device may be an optical system
which splits a short wavelength laser light of the short wavelength
laser. Accordingly, only a single short wavelength laser is
necessary.
According to a further aspect of the method of the present
invention, the thin film may be formed on an object by using an
oxide soft magnetic material as the target. Therefore, it is
possible to form a thin film of excellent crystallizability with
less oxygen deficiency, thereby achieving a soft magnetic thin film
of low coercive force.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will
become clear from the following description of preferred
embodiments thereof made with reference to the accompanying
drawings, in which:
FIG. 1 is a schematic diagram of a first embodiment of a laser
ablation device according to the present invention;
FIG. 2 shows the operation of the device of FIG. 1;
FIG. 3 is a schematic diagram of a modified form of the first
embodiment of the laser ablation device;
FIG. 4 is a schematic diagram of a second embodiment of a laser
ablation device according to the present invention;
FIG. 5 shows the operation of the device of FIG. 4; and
FIG. 6 is a schematic diagram of a conventional laser ablation
device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the description of the present invention proceeds, it is to
be noted that like parts are designated by like reference numerals
throughout the accompanying drawings.
The first embodiments of a laser ablation device and a method for
forming a thin film on an object using an oxide soft magnetic
material as a target, will be described with reference to FIG.
1.
In FIG. 1, the preferred embodiment of the laser ablation device
includes an optical system, a vacuum chamber 1, an air discharging
device 5 for evacuating the chamber 1, a gas introduction port 6
for introducing an oxidating gas (O.sub.2, N.sub.2 O or the like),
a light-transmittable window 7 through which a laser light from an
excimer laser passes and which is made of synthetic crystal, for
example, a target holder 60 arranged in the vacuum chamber 1 for
holding a target 2 made of a sintered body of Ni-Zn-ferrite which
is an oxide film forming material (in some cases, the target holder
may be omitted), a substrate holder 3 confronting the target holder
60 for holding a substrate 4 as an object on which a thin film is
to be formed, and a short wavelength laser 8 for irradiating the
target 2 in the vacuum chamber 1 with laser light of a short
wavelength, the laser light passing through the light-transmittable
window 7 from outside the vacuum chamber 1. The optical system
includes a half mirror 11, mirrors 9 and 12, and a lens 10. Some of
the short wavelength laser light from the short wavelength laser 8
passes through the half mirror 11, is reflected by the mirror 9, is
condensed by the lens 10, and irradiates the target 2 as a short
wavelength laser light 13 having a very small diameter directed
through the light-transmittable window 7. The remaining part of the
laser light from the short wavelength laser 8 is reflected by the
half mirror 11 and the mirror 12 and irradiates the substrate 4 as
a short wavelength laser light 14 having a certain large diameter.
As an example, the short wavelength laser 8 comprises a KrF excimer
laser emitting laser light having a wavelength of 248 mm.
Alternatively, an ArF excimer laser or an XeCl excimer laser may be
used as the short wavelength laser 8. A heater 63 is incorporated
inside the substrate holder 3 to heat the substrate 4 thereon to a
predetermined temperature. The position at which the short
wavelength laser light 13 condensed by the lens 10 is incident on
the target 2 can be changed by a mechanism provided for moving the
short wavelength laser light 13 or the target 2.
Now, the operation of the laser ablation device will be described
with reference to FIGS. 1 and 2.
In FIGS. 1 and 2, the target 2 made of a sintered body (although
not restricted to a sintered body) of Ni-Zn-ferrite as a film
forming material is held by the target holder 60. The substrate 4
is supported by the substrate holder 3. After the vacuum chamber 1
is evacuated by the discharging device 5 to a predetermined degree
of vacuum, an oxidative gas such as O.sub.2 gas or N.sub.2 O gas is
supplied through the gas introduction port 6 to maintain the vacuum
chamber 1 at a predetermined degree of vacuum. In this state, when
the short wavelength laser light is emitted from the short
wavelength laser 8, art of the laser light passes through the half
mirror 11 and is reflected by the mirror 9, condensed by the lens
10, and irradiates the target 2 as the short wavelength laser light
13 directed through the light-transmittable window 7. The remaining
part of the laser light is reflected by the half mirror 11 and the
mirror 12 and irradiates the substrate 4 as a short wavelength
laser light 14. As a result, ablated particles 15 of the sintered
body of Ni-Zn-ferrite constituting the target 2 are projected from
the target 2. These particles migrate over or move about the
substrate 4 held by the substrate holder 3 and form a thin film 16.
When the thin film 16 is being formed, the migrating ablated
particles 17 are excited by the short wavelength laser light 14
irradiating the substrate 4. Therefore, the ablated particles 17
easily react with O.sub.2 molecules 18 of the oxidating gas, etc.
in the vicinity of the substrate 4.
Accordingly, the oxygen deficiency in the formed thin film is
reduced. Since the migrating ablated particles 17 are excited
during deposition, the crystallizability of the formed thin film 16
is improved. Although the substrate 4 is heated to about
300.degree. C. by the built-in heater 63, it is possible to obtain
a film of Ni-Zn-ferrite of a spinel single structure-crystal.
Since the short wavelength laser light 14 irradiates the substrate
4 simultaneously with the ablation, the coercive force of the
Ni-Zn-ferrite film is improved from 100 Oe (oersted), in the case
without the short wavelength laser light, to 20 Oe or lower.
In the instant embodiment, since the short wavelength laser light
14 irradiating the substrate 4 is not condensed by any lens, the
intensity of the laser light 14 is approximately 1/10-1/100 of that
of the short wavelength laser light 13 condensed by the lens 10.
Therefore, there is no ablation at the substrate 4. However, if the
intensity of the short wavelength laser light 14 is too strong,
that is, the intensity of the laser light 14 is more than 1/10 of
that of the short wavelength laser light 13, Zn or the like is
ablated again from the film 16, whereby the magnetic properties of
the film 16 are eventually deteriorated. If the intensity of the
short wavelength laser light 14 is too weak, that is, the intensity
of the laser light 14 is less than 1/100 of that of the short
wavelength laser light 13, the above-desired effects cannot be
obtained.
Although the short wavelength laser light 14 is separated from the
short wavelength laser light 13 by using the half mirror 11, it is
possible to use a separate short wavelength laser 8b of
0.05J/cm.sup.2 for irradiating the substrate with a short
wavelength laser light at approximately the same time the target is
irradiated with laser light from a short wavelength laser 8a of
1J/cm.sup.2, as shown in FIG. 3. The same effect as in the
above-described embodiment can be achieved.
A second embodiment of a laser ablation device and film forming
method according to the present invention will be described below.
The structure of the device will first be described with reference
to FIG. 4.
The second embodiment is different from the first embodiment in
that instead of irradiating the substrate 4 with the short
wavelength laser light 14, a short wavelength laser light 31 is
reflected by the half mirror 11 to pass through the
light-transmittable window 7 into the vicinity (e.g. within 30 mm
of the substrate 22.
The operation of the above-described laser ablation device is
similar to that of the first embodiment. Only the difference
between the operations will be described with reference to FIGS. 4
and 5.
When the short wavelength laser light is emitted from the short
wavelength laser 8, part of the laser light passes through the half
mirror 11, is reflected by the mirror 9 and condensed by the lens
10, and finally reaches the target 2, as short wavelength laser
light 13, via the light-transmittable window 7. The remaining part
of the laser light 30 passes in the vicinity (within 30 mm) of the
substrate 4 as short wavelength laser light 31 after it is
reflected by the half mirror 11 through the light-transmittable
window 7. As a result, ablated particles 15 of the sintered body of
Ni-Zn-ferrite constituting the target 2 are projected from the
target 2, so that a thin film 16 is formed from the ablated
particles 15 migrating over or moving about the substrate 4 held by
the substrate holder 3. At the time this thin film 16 is formed,
since the short wavelength laser light 31 passes in the vicinity of
the substrate 4, the ablated particles 15 are excited before
reaching the substrate 4, thereby improving the reactivity.
Accordingly, the reaction of the ablated particles 15 with O.sub.2
molecules 18 of the oxidating gas in the vicinity of the substrate
4 is promoted, thus reducing the oxygen deficiency of the thin film
16. At the same time, O.sub.2 molecules 18 in the vicinity of the
substrate 4 are excited by the short wavelength laser light 31 into
O radicals 35, and therefore, the reaction of the O.sub.2 molecules
18 with the ablated particles 15 or the excited ablated particles
is enhanced, whereby the oxygen deficiency of the thin film 16 is
reduced.
Further, since the excited ablated particles 15 are deposited on
the substrate 4, the crystallizability of the thin film 16 is
improved. Even when the substrate is kept at 300.degree. C. or so
(through heating by the built-in heater 63 of the substrate holder
3), it is possible to obtain a Ni-Zn-ferrite film of a spinel
single structure-crystal. That is, the magnetic properties are
improved, similar to the preceding embodiment.
Although Ni-Zn-ferrite is used as a film forming material in the
above-described embodiments, the present invention is not limited
to an Ni-Zn-ferrite target. The same oxidation accelerating effect
and the improvement of crystallizability are attained so long as
the material is an oxide. Moreover, the oxidating gas is not
limited to O.sub.2 or N.sub.2 O.
According to the first embodiment of the laser ablation device of
the present invention, a thin film of an oxide is formed by the
ablating effect of the laser light, and the ablated particles
migrating over an object are excited by short wavelength laser
light irradiating the object. Therefore, the ablated particles
readily react with the oxidating gas in the vicinity of the object,
the oxidation is accelerated and the oxygen deficiency of the
formed film is reduced, and the crystallizability is improved.
Annealing at high temperatures for the purpose of improving the
oxidation state becomes unnecessary.
According to the second embodiment of the laser ablation device of
the present invention, a thin film of an oxide is formed by the
ablating effect of the laser light, the short wavelength laser
light passes parallel to and in the vicinity of the surface of an
object, and the ablated particles before reaching the object are
excited and separated from the oxidating gas in the vicinity of the
object to generate O radicals. Therefore, the oxidation between the
ablated particles and O radicals is enhanced and the oxygen
deficiency of the formed film is reduced, and the crystallizability
is improved. High-temperature annealing for the purpose of
improving the oxidation state is thus not required.
In the first and second embodiments of the present invention, the
short wavelength laser light irradiating device includes an optical
system for splitting the short wavelength laser light emitted by
the short wavelength laser, and accordingly, only a single short
wavelength laser is used. Additionally, since the short wavelength
laser light 14 is separated from the short wavelength laser light
13 by the half mirror 11, the operational effects of the laser
lights 13 and 14 are synchronized.
According to the second embodiment of the thin film forming method
of the present invention, the above laser ablation device is used
to form a thin film on the object from a soft magnetic oxide
material employed as a target. Therefore, a thin film of good
crystallizability with little oxygen deficiency is obtained. A
high-temperature annealing process conventionally required for
improving the oxidation state is not used, yet a soft magnetic thin
film of low coercive force is obtained.
Although the present invention has been fully described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications will become apparent to those skilled in the art.
Such changes and modifications are to be understood as included
within the scope of the present invention as defined by the
appended claims unless they otherwise depart therefrom.
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